1. Field of the Invention
The present invention relates to an inner-earn system, distributor type fuel injection pump used for supplying fuel to engines such as diesel engines, i.e., a fuel injection pump in which a plunger makes reciprocal movement against a rotating reenter, which is synchronized with the engine, in the direction of the radius of the rotating member.
2. Description of the Related Art
Distributor type fuel injection pumps which employ the inner-earn system in the known art include those disclosed on page 2 and page 4 and in FIG. 1 and FIG. 7 of Japanese Unexamined Patent Publication No. S59-110835. In this type of pump, an inner-cam ring 1 is provided concentrically around a fuel distribution rotating member 4 (rotating member) inside a fuel chamber 121 (chamber) and on the earn surface, which is formed on the inside of the inner-cam ring 1, compression plungers 21, 22 are provided via rolling elements 23, 24 (rollers) and shoes 25, 26. The compression plungers 21, 22 make a reciprocal movement in the direction of the radius of the fuel distribution rotating member 4. A pump chamber 2 (compression space) whose volumetric capacity is changed by the compression plungers 21, 22, intake holes 51, 54 for drawing the fuel in to the pump chamber 2 during the intake process, a distribution port 6, for sending out the fuel that has been pressurized in the pump chamber 2 during the compression process, and overflow ports 71, 74 for cutting off the fuel supply are formed in the fuel distribution rotating member 4, which is externally fitted with an oil-tight ring-like member 7 (control sleeve), that covers the overflow ports 71 and 74. A diagonal lead groove portion 10 for cut off is formed on the inner surface of the ring-like member 7 and by adjusting the position of the ring-like member 7 in the axial direction of the shaft with a linear solenoid 81, the cutoff timing during the compression process (the timing with which the overflow ports opens into the diagonal lead groove portion to release compressed fuel into the fuel chamber 121) can be varied to change the fuel injection quantity.
In addition, in FIG. 1 of Japanese Unexamined Patent Publication No. S59-65523, a distributor type fuel injection pump employing the inner-cam system is disclosed, in which fuel that has been taken in by a feed pump is decompressed with a constriction 23 and then induced to a low pressure fuel reservoir or chamber 24 where shoes 4 provided at the base end of the plungers 3, rollers 5 supported by the shoes 4 and a cam ring 6 with which, the rollers are in contact, are provided. With this fuel injection pump, the fuel in the low pressure fuel reservoir 24 can be supplied to the intake port 20 of the rotating member 1 and, at the same time, it can be supplied to the space enclosed by the cam ring 6 and the rotating member 1. In this structure too, while the fuel which is retained in the rotor 1 is compressed during the compression process, the injection is cut off when the compressed fuel escapes via the bypass pert 36.
However, when the space into which the fuel flows during this cut off period communicates with the space surrounding the rollers, as in the fuel injection pumps described above, even if the fuel pressure is reduced by the constriction 23, as in Japanese Publication No. S59-65523, the temperature inside the chamber increases, as the high-temperature, high pressure fuel that has been compressed during the compression process, flows out to the chamber. This results in insufficient cooling of the contact area between the cam ring and the rollers and also the contact area between the rollers and the shoes, where friction heat tends to be generated.